Note 14 - Merom Acquisition (Details Textual) - USD ($) $ in Thousands		3 Months Ended
	Feb. 14, 2022	Mar. 31, 2023	Mar. 31, 2022
Operating Expenses		$ 29,233	$ (8,677)
Merom Acquisition [Member]
Capacity Payment Reductions	$ 15,000
Purchase Obligation, Total	7,200
Business Acquisition, Purchase of Coal Inventory	17,000
Business Acquisition, Purchase of Coal Inventory, Initial Payment	5,400
Business Acquisition, Transaction Costs	2,900
Contract with Customer, Liability	184,500	127,900
Contract with Customer, Liability, Revenue Recognized		33,300
Contract with Customer, Asset, after Allowance for Credit Loss	$ 34,300	6,200
Operating Expenses		17,800
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Inventory		$ 4,400